The present invention generally relates to manufacturing optical fiber cables and, more particularly, to improving the consistency of the reverse oscillating lay of the cables during the manufacturing process to thereby improve the quality of the cables and prevent them from failing during use.
It is known in the optical fiber cable manufacturing industry that reverse oscillating lay (ROL) inconsistency during the cable manufacturing process, particularly in regard to high-fiber-count (HFC) cables, results in non-uniform distribution of the mechanical load and stress on the cable throughout its entire length. This non-uniform distribution of mechanical load/stress on the cable during the manufacturing process often results in the cable exhibiting high optical loss during mechanical and environmental qualification tests, which is regarded as a failure in the cable.
FIG. 1 is an ROL machine of the type that is typically used during the HFC cable manufacturing process to reduce the non-uniform distribution of mechanical load/stress (hereinafter referred to solely as xe2x80x9cstressxe2x80x9d) on the cable as it is being manufactured. A HFC cable is a cable that comprises a plurality of subunits 1, typically three to twelve, each of which comprises a plurality of coated optical fibers (not shown). During the HFC cable manufacturing process, the subunits 1 of the HFC cable are pulled through holes 2 formed in a series of reverse oscillating plates 3 as adjacent reverse oscillating plates are rotated in the same direction, but at incrementally increasing angles of rotation. At a particular point during the rotations of any two adjacent plates 3, a predetermined amount of twist is added to the core of the HFC cable. At this point, the direction in which each of the plates is being rotated reverses, and the plates rotate oppositely until the same amount of twist has been added to the core of the HFC cable in the opposite direction. The twisting of the HFC cable in this manner as it is being pulled is intended to equalize the distribution of stress on the cable over its length.
In current practices, after the HFC cable exits the ROL machine, the HFC cable generally is pulled through, respectively, a powder machine (for certain type of cables), a set of torsion rolls, which helps to keep the subunits 1 together, an extruder, a water trough and a main capstan. The extruder extrudes a material onto the cable that is to form the outer jacket of the cable. The water trough cools and solidifies the extruded material to form the outer jacket, which bundles and holds the subunits 1 of the HFC cable together. The cable is then pulled through the main capstan. The main capstan is monitored by a feedback system that controls the speed of the main capstan to control the speed at which the cable is pulled along the manufacturing line.
One of the problems associated with this HFC manufacturing technique is that it does not ensure that ROL is consistently maintained. Once the cable passes through the extruder, there is nothing to maintain the ROL, which often times results in the cable failing during testing or usage.
Accordingly, a need exists for a method, an apparatus and a system for ensuring that the ROL is consistently maintained during the manufacturing process, thereby decreasing or eliminating the amount of cable that is flawed due to inconsistent ROL. In accordance with the present invention, a method, apparatus and system are provided for improving ROL consistency during an optical fiber cable manufacturing process. The apparatus of the present invention comprises a torque capstan that receives an optical fiber cable from an ROL machine that places reverse-oscillating lay on the core of an optical fiber cable, but also generates some undesirable fluctuating back-tension in a direction opposite a direction in which the optical fiber cable is being pulled during optical cable manufacturing. The optical fiber cable comprises a plurality of subunit cables. A drive system of the apparatus is coupled to the torque capstan and controls the torque capstan. The drive system is controlled by a control system of the apparatus to cause the torque capstan to apply a certain amount of force to the optical fiber cable in a direction substantially parallel to the direction in which the optical fiber cable is being pulled during the optical fiber manufacturing process. The certain amount of force applied to the optical fiber cable by the torque capstan reduces back-tension on the optical fiber cable to enable ROL consistency to be maintained during the optical fiber cable manufacturing process.
The system of the present invention comprises the utilization of the apparatus of the present invention in combination with the method of the present invention in accordance with the preferred embodiment to reduce back-tension on the optical fiber cable in order to maintain ROL consistency.
The method of the present invention comprises the steps of delivering an optical fiber cable from a reverse oscillating lay (ROL) machine to a torque capstan, and utilizing a control system to control a drive system that is coupled to the torque capstan to cause the torque capstan to apply a certain amount of force to the optical fiber cable in a direction substantially parallel to the direction in which the optical fiber cable is being pulled, thereby reducing back-tension on the optical fiber cable in order to maintain ROL consistency.
These and other features and advantages of the present invention will become apparent from the following description, drawings and claims.